This invention relates to a hinge assembly used for turnably connecting, for example, a main body and a cover member of a cellular telephone.
FIGS. 10 and 11 show one example of a cellular telephone in which a hinge assembly of this type is used This cellular telephone A comprises a main body B and a cover member C turnably connected to the main body B through a hinge assembly (not shown). The cover member C can be turned at least between a closed position I where it contacts the main body B to close the front surface of the main body B and an open position III via a neutral position II.
The conventional hinge assembly used in the above cellular telephone A comprises a hinge main body and a hinge pin turnably connected to the hinge main body. One of the hinge main body and the hinge pin is connected to the main body B of the cellular telephone and the other is connected to the cover member C. By this, the cover member C is turnably connected to the main body B about a rotation axis L (this rotation axis L is in alignment with an axis of the hinge pin).
The hinge main body is provided with a plate spring (resilient member), and a cam portion subject to press contact by the plate spring, is formed on an outer peripheral surface of the hinge pin. The cam portion includes a neutral portion, and a first and a second cam surface mutually reversely extending in a circumferential direction of the hinge pine from this neutral portion. The neutral portion is arranged such that when the cover member C is turned to the neutral position II, the neutral portion contacts the plate spring. The first cam portion is arranged such that when the cover member C is located between the closed position I and the neutral position II, the first cam portion contacts the plate spring, while the second cam portion is arranged such that when the cover member C is located between the neutral position II and the open position III, the second cam portion contacts the plate spring.
The plate spring does not rotationally bias the hinge pin when it is in contact with the neutral portion but it rotation biases the hinge pin in a direction as indicated by an arrow X of FIG. 11 when it is in contact with the first cam surface. When the plate spring is in contact with the second cam surface, it rotation biases the hinge pin in a direction as indicated by an arrow Y of FIG. 11. Hence, although the cover member C maintains a stop state in the neutral position, but it is turned to the closed position or the open position by the plate spring when it is moved away from the neutral position.
The above-mentioned conventional hinge assembly has difficulty in solving the following two problems simultaneously.
The cellular telephone A is desirably designed such that when the cover member C is moved away from the neutral position II, it is immediately turned to the closed position I or the open position III. This can be achieved by reducing the radii of curvature of the first and second cam surfaces, of the hinge assembly. However, if the radii of curvature of the first and second cam surfaces is reduced, a resilient deformation amount of the plate spring is increased against a predetermined rotation angle of the cover member C. For this reason, the plate spring is deteriorated with the passage of time and loses resiliency. As a result, play or rattling occurs between the cover member C and the main body B when the cover member C is in the closed position or in the open position. Or the plate spring is broken.
In contrast, if the radii of curvature of the first and second cam surfaces are increased, the resilient deformation amount of the plate spring due to rotation of the cover member C can be reduced and therefore, the plate spring can be prevented from being deteriorated with the passage of time. However, in that case, the turning force of the plate spring exerted to the cover member C is reduced when the cover member C is located in the nearby portion of the neutral position. It gives arise to another problem that the cover member C cannot be turned to the closed position I or the open position III by the plate spring and the cover member C is turned by hand until the cover member C is greatly moved away from the neutral position.
In order to solve the above problems, the features of the present invention reside in a hinge assembly comprising a hinge main body and a hinge pin turnably supported by the hinge main body, the hinge main body being provided with a resilient member, the hinge pin being provided on an outer periphery thereof with a cam portion which is to be press contacted by the resilient member, the cam portion including a neutral portion for directing the pressing force of the resilient member to a center of rotation of the hinge pin, and a first and a second cam surface mutually reversely extending in a circumferential direction of the hinge pin from the neutral position and for converting the pressing force of the resilient member into a rotation torque for mutually reversely turning the hinge pin,
wherein radii of curvature of nearby portions of the neutral portion (hereinafter simply referred to as the xe2x80x9cnearby portions) of the first and second cam surfaces are set to be smaller than radii of curvature of portions (hereinafter referred to as the xe2x80x9cseparated portionsxe2x80x9d) which follow the nearby portions of the first and second cam surfaces.
In this case, it is preferred that the separated portions of the first and second cam surfaces are composed of a mutually identical arcuate surface, the neutral portion and the nearby portions are composed of an arcuate surface having a smaller radius of curvature than the radii of curvature of the arcuate surfaces forming the separated portions, and a center of curvature of the arcuate surface composing the neutral portion and the nearby portions is arranged on a line passing through the center of curvature of the arcuate surfaces forming the separated portions and orthogonal to the center of rotation of the hinge pin and at a place more separated from the rotation axis than the center of curvature of the arcuate surfaces composing the separated portions.
It is also preferred that the cam portion further includes a turn restricting portion formed on an outer peripheral surface of the hinge pin following at least one of the first and second cam surfaces of the hinge pin and capable of contacting the resilient member at least at two points separated in a circumferential direction of the hinge pin, thereby maintaining the hinge pin in a predetermined rotation position with moderation.
Moreover, it is preferred that two of the cam portions are arranged in point symmetry about the rotation axis of the hinge pin, and two of the resilient members are arranged on cam surfaces of the cam portions in such a manner as to correspond to each other.